How to Get Rid of Plaster Bagworms In Your Home
Little grey bugs attached to the walls? Learn what they are and how to exterminate them
Plaster bagworms (Phereoeca uterella) are small case-bearing moth larvae that build flat, oval-shaped silk cases. They are commonly found on stucco walls, ceilings, and inside garages. They are common throughout the world as you get closer to the equator, from the southeastern United States to Central America and Asia – anywhere humidity is high and spider populations are abundant. Plaster bagworms are harmless to humans and pets, do no structural damage to homes, and feed primarily on spider webs, dust, and dead insects. Because the larvae live inside protective silk cases, spraying insecticides are often ineffective. Effective control is mostly a matter of cleaning – vacuum and dust regularly, reducing indoor humidity, sweep away cobwebs, and limit exterior lighting that attracts adult moths. Honestly: a vacuum and a regular cleaning routine handle most plaster bagworm problems on their own. Pest control has a supporting role, not a starring one.
Do you see small grey bugs hanging on your walls or ceiling? These are Bagworms & Casebearers
What are these small grey bugs that looks like pieces of dirt?
Have you noticed small greyish to white colored bugs hanging on your walls or ceiling? Or maybe it looks like some kind of egg sac? What you are likely seeing is a cocoon-like case, with an insect hidden inside. The common name for these creatures is a Plaster Bagworm, however, it is more etymologically accurate to refer to them as Household Case Bearers (Phereoeca uterella). Dust Worms are another common name for these creatures. The long oval-shaped little case or “bag” that is most commonly found in homes and garages are the cocoon created by the larval or caterpillar stage of a moth.
Despite ultimately transforming into a moth, it is not typical to have significant numbers of moths visibly flying about the house. If this is the case, it is more likely you may have an infestation of Indian Meal Moths.
WATCH: a plaster bagworm moving across a plate in Port St. Lucie.
What do plaster bagworms eat?
Plaster bagworms’ primary food source are spider webs. They will also feed on dead insects, human and pet hair, lint, dust, and occasionally wool fibers. Spider webs are the main reason these larvae climb to walls and ceilings — they’re heading toward their primary food source.
Removing spider webs, dusting and vacuuming are critical to controlling bagworms. It’s a pattern we see often: an out-of-town family member visits their elderly parents and finds a bagworm infestation in the home. When elderly residents are no longer able to do hard-to-reach cleaning, bagworm populations tend to rise simply because of the abundance of food (cobwebs and dust). A professional cleaning a few times a year can go a long way toward prevention.
Why are plaster bagworms in my house?
Like people, insects have basic needs such as food and shelter, that must be met in order to survive. For Plaster Bagworms and Household Casebearer, those needs are VERY basic. Their diet consists of old spider webs, dead insects, and even human hair. Part of the reason these insects are found stuck to walls and ceilings is that they have climbed up there to be closer to the cobwebs they feed on. It doesn’t take much to satisfy a hungry Plaster Bagworm.
Household Casebearers and Plaster Bagworms are common throughout the Southeastern United States. Thriving in warm and humid climates, they are a particular nuisance in Florida where their population in and around homes can become quite high if some mitigating measures aren’t taken.
It’s very common to find Plaster Bagworms and Household Casebearers attached to the exterior stucco, vinyl or wood siding of homes as well.
Bagworms and Casebearers will eat wool, but they will not eat cotton or nylon.
How can I get rid of Plaster Bagworms in my home?
- Thorough Cleaning
Because both their diet and the material used to create their cocoon is basically tiny bits of organic material, thorough and consistent cleaning can remove both the food and shelter they need to survive and result in a decreased population. This, however, can be a bit difficult in areas such as garages, carports, patio, and lanai areas. Nevertheless, sweeping down cobwebs, and blowing out accumulated debris in garages and porches will help prevent a thriving Casebearer population. - Reduce Outside Lighting
Another good tip for preventing Plaster Bagworms is to reduce outside lighting. Ultimately, these little creatures are moths. Moths are notoriously attracted to porch lights. If moths are attached by a light left on in the garage, or a security light on the side of the house, you are attracting them to your home. It is ultimately these adult female moths that will lay the eggs that eventually turn into the annoying little egg sac-like creature stuck to your ceiling. - Keep Temps & Humidity Moderate
Obviously, there is little that can be done in this regard in outside areas. There is a reason, though, that they have the name HOUSEHOLD Casebearer. They are certainly capable of surviving inside homes. Another reason why you’ll find these weird little bugs in these areas is that they, like all insects, prefer warmth and humidity. Plaster Bagworm populations will be higher in homes where the inside temperature is kept above 80 degrees. If, like many Floridians, your home is only occupied part of the year, be sure to keep your A/C running even when you are away. Click here for tips on things you can do for free that will prevent pest problems. - Vacuuming
Often homeowners will sweep down the caterpillar cases along with any cobwebs nearby. While this can be somewhat helpful, it is limited in its effectiveness in two way.
1) The moth’s larvae are well protected inside their cocoon.
2) The material they consume, spiderwebs and the remains of dead insects caught in them, simply end up on the floor, still easily available for the Plaster Bagworm to eat.
By vacuuming, whether, with a household vacuum or a shop-vac, both the bagworm itself and the material it eats are effectively removed from the premises. Remember to empty the contents of the vacuum into a garbage bag and take the bag out of the house, or you may just end up with a bunch of well-fed moths living in your vacuum.
Do I need to call an exterminator to get rid of dust worms?
In most cases, a thorough physical cleaning is the best way to get rid of the dust worms in your house. If you see a large infestation of plaster bagworms in your home (multiple insects on the walls and ceilings) then it is time to call professional pest control. Preventative insect control both indoors and outdoors will help prevent these and other bugs from making your home their home. With two local offices in Martin and Port St Lucie counties, we provide pest control in Plam City, Port St Lucie, FL and surrounding communities.
Plaster bagworm crawling across a floor in Port St. Lucie.
Frequently Asked Questions
Are plaster bagworms harmful to humans or pets?
No. Plaster bagworms do not bite, sting, or spread disease. They are largely just an aesthetic pest. There is the potential to harm wool fabrics, but even this is relatively minimal compared to other pests such as carpet beetles.
Can plaster bagworms damage my home?
Plaster bagworms cause no structural damage. They do not eat wood, drywall, or other building materials. They may damage wool fabrics if a population is left unchecked, but they do not harm cotton or synthetic fabrics, and they do not damage paint.
Why do I suddenly have so many plaster bagworms?
Plaster bagworms reproduce quickly in humid climates such as Florida or Singapore. A small population can become hundreds within a couple of months if conditions are favorable. Common triggers: increased spider webs (their food source), higher indoor humidity, reduced cleaning frequency, and exterior lighting attracting adult moths to the home.
Will plaster bagworms go away on their own?
No. Without intervention, populations will continue to grow. Plaster bagworm infestations are conditions based — reducing conducive conditions (spider webs, humidity, dust) will be what ultimately leads to control. It is worth noting: The old casings will need to be manually removed. Garages often appear to have serious bagworm issues when in fact the walls have never just been swept and the casings have accumulated over many years.
I cleaned and vacuumed but the plaster bagworms came back. Why?
As mentioned above, be sure you have removed all the existing bagworm casings. These will not evaporate on their own and if not removed, you may mistake an old case for a new problem. Beyond that, when cleaning you may have missed some eggs or larvae. If windows or doors are open, it’s possible new moths have entered. Open windows will also increase humidity, further aiding the bagworms. Spider webs, too, will come back quickly without an appropriate treatment, and their cobwebs will further facilitate bagworm populations.
Are plaster bagworms the same as pantry moths?
No. They are related (both are moths) but are very different pests. Pantry moths infest stored food. Plaster bagworms feed on spider webs, household debris, and occasionally wool. They do not infest pantries or food storage areas. The treatment procedures for each are dramatically different.
In what regions are plaster bagworms common?
Plaster bagworms are common throughout humid subtropical and tropical climates — including the southeastern United States (Florida, Georgia, Alabama, Louisiana, Texas), the Caribbean, South America, and Asia – in particular Singapore. They thrive wherever indoor humidity stays high and spider populations are abundant. Older homes tend to have more persistent problems, but newer construction is not immune.
How long does it take to get rid of plaster bagworms?
With consistent food-source removal and humidity control, most homeowners see significant reduction almost immediately. However totally elimination typically takes 6 to 8 weeks because the bagworm lifecycle runs about 74 days — newly hatching larvae from existing eggs continue to appear for several weeks after the adults are gone. Keep in mind: If you have taken all of the standard steps to eliminate food sources and humidity issues and the bagworm problem persists, this may be a canary in the coal mine that there is a more serious moisture issue inside the home.
— Shane Green, owner of Green Pest Services. If you are having a plaster bagworm problem, remember the answer is more often a vacuum than an exterminator. GPS has been doing pest control on Florida’s Treasure Coast since 2016. If you are in Port St Lucie or Palm City, check out our reviews! We would love to serve you in any way we can.